Carl Witthoft <c...@witthoft.com> writes:
> Hi,
> While playing with quantile-quantile plots, I wrote up some code which
> plots something strangely different. Here's the pseudocode:
>
> testhist <- hist(sample_data)
> refhist <- hist(rnorm(n, mean=0,sd=1)) # for some large-ish n
> cumtest <- cumsum(testhist)
> cumref <- cumsum(refhist)
>
> plot(cumref,cumtest)
Sounds like a 'pp-plot'. See
http://en.wikipedia.org/wiki/P-P_plot
Why not provide reproducible code?
Chuck
>
> This produces a straight line of slope 1 for a sample with the same
> parameters as the reference sample, and produces S-curves for samples
> with different sigmas. A sample with nonzero mean looks almost
> exponential (or logarithmic, depending on the sign of the mean).
>
> So my question is: is there a name for this sort of plot, and is it
> of any real use in statistical analysis?
>
> thanks.
> Carl
--
Charles C. Berry Dept of Family/Preventive Medicine
cberry at ucsd edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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